Float and a floatable structure

ABSTRACT

A float ( 1 ) comprising a hollow pneumatically pressurisable ovoid shell ( 5 ) is provided with a damping plate ( 12 ) extending laterally outwardly around the shell ( 5 ) for damping vertical upward and downward movement of the float in water during stormy conditions, thereby minimising the effect of the buoyant upward propulsion force acting on the float when the float is submerged in stormy conditions. A keel ( 18 ) extends downwardly from the float ( 5 ) for minimising rolling movement of the float ( 1 ). A pair of coupling plates ( 22 ) extending from front and rear ends ( 19,20 ) of the shell ( 5 ) facilitate coupling of the float ( 1 ) between a pair of spaced apart tethering ropes used in mussel growing. A plurality of the floats ( 1 ) may be secured between a pair of spaced apart tethering ropes at spaced apart intervals along the tethering ropes for supporting the tethering ropes so that crop ropes impregnated with mussel spawn may be suspended from the tethering ropes for growing mussels. A navigational buoy ( 60 ) is also disclosed, which comprises a lower float ( 61 ) and a pillar ( 62 ) extending upwardly therefrom for carrying navigational and other instrumentation.

This is a divisional of U.S. Ser. No. 11/913,506, filed Mar. 6, 2008,which is a national stage of PCT/IE2006/000044 filed May 3, 2006, whichclaims priority from Ireland S20050273 filed May 4, 2005, and IrelandS2006/0215 filed Mar. 20, 2006, the disclosures of which areincorporated herein in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a float, such as a float for suspendingan article submersed in water, or a float of the type used as anavigational buoy or for carrying instrumentation, such as weathermonitoring instrumentation, although the invention is not limited tosuch floats. The invention is also directed towards a floatablestructure of the type suitable for use as a navigational buoy or forcarrying instrumentation, and the invention also relates to a method fordamping buoyant movement of a float in water, as well as to a method forgrowing marine molluscs.

Floats for suspending articles submersed in water, for example, in thesea, lakes, rivers and the like are well known. Such floats, arecommonly used in the commercial mussel growing industry for suspendingropes impregnated with mussel spawn in the sea, and mussels which growon the ropes are harvested by withdrawing the ropes from the water. Suchropes are commonly referred to as crop ropes. In general, a plurality ofsuch floats are secured between a pair of spaced apart tethering ropes,at spaced apart intervals along the tethering ropes, and the crop ropesare secured to and suspended from the tethering ropes at spaced apartintervals along the tethering ropes between the floats, so that the cropropes depend downwardly into the sea. Respective opposite ends of thetethering ropes are secured to suitable moorings. Such arrangements offloats will be well known to those skilled in the art. In general, thefloats are of cylindrical construction terminating in opposite domedends. Coupling members extend axially from the domed ends, and thespaced apart tethering ropes are secured to the coupling members, sothat the floats extend between the tethering ropes with their respectivecentral axes extending perpendicularly to the tethering ropes.

Typically, the floats are of plastic material, and may be foam filled,or air filled. Such floats known heretofore suffer from a seriousdisadvantage. In general, such floats are suitable for use in shelteredwaters only; they are unsuitable for use in open unprotected waters.When subjected to waves in open unprotected water, and in particular,when subjected to relatively large waves which occur in stormyconditions, and which can be up to ten metres in height and greater, thefloats become submerged, and can be submerged to depths of up to twentymetres and greater. This is particularly so as the mussels grow on thecrop ropes and the crop ropes become increasingly heavier. Whensubmerged to such depths there is a danger of the floats collapsing, andwhere such floats do not collapse, the buoyant upward force on thefloats tend to propel the floats out of the water to heights above thewater which can be up to four metres. This is totally undesirable, sincethe rapid propulsion of the floats out of the water and their suddenreturn tends to shake the mussels from the crop ropes, and the largerthe mussels, the greater is the danger of the mussels being shaken fromthe crop ropes.

There is therefore a need for a float which addresses this problem, andsignificantly reduces the danger of mussels being shaken from the cropropes.

Floats are also commonly used for carrying instrumentation, for example,instrumentation for monitoring weather conditions at sea, on lakes andthe like, such as wind speed and direction, rainfall amounts,temperature, humidity, air pressure and the like. Floats are alsocommonly used as navigational buoys for marking shipping lanes and areaswhich are hazardous for shipping. All such floats are secured by anchorropes, cables or chains to seabed moorings, and suffer from a similarproblem to that discussed above, in that in stormy conditions, whensubjected to relatively large waves, the navigational buoys or floatscarrying instrumentation can be submerged to depths of up to twentymetres or greater, and the buoyant upward force at such depths can besufficient to propel the float upwardly with a sufficient force to causethe mooring rope or ropes to snap, resulting in loss of the float.Additionally, where floats are used for carrying instrumentation, forexample, weather monitoring and environmental monitoringinstrumentation, or indeed a light transmitting beacon, the upwardbuoyant forces to which such floats are subjected during stormyconditions may be sufficient to damage the instrumentation, beacons orother such items carried on the float.

Accordingly, there is a need for a float and a navigational buoy as wellas a floatable structure which address the problems discussed above.

SUMMARY OF THE INVENTION

The present invention is directed towards providing such a float and anavigational buoy, and the invention is also directed towards providinga floatable structure comprising the float, which is suitable for use asa navigational buoy or for carrying instrumentation, and the inventionis also directed towards a method for damping buoyant movement of afloat in water, and to a method for growing marine molluscs.

According to the invention there is provided a float comprising adamping means extending laterally from the float for damping buoyantmovement of the float in water in a generally vertical direction.

Preferably, the damping means extends outwardly on opposite sides of thefloat. Advantageously, the damping means extends completely around thefloat. Ideally, the float defines a submersible surface, and the dampingmeans extends from the submersible surface.

In one embodiment of the invention the damping means damps upwardbuoyant movement of the float. Preferably, the damping means also dampsdownward movement of the float. Advantageously, the damping means dampsrolling movement of the float. Preferably, the damping means also dampspitching movement of the float.

In one embodiment of the invention the damping means defines a firstplane. Preferably, the first plane extends in use substantiallyhorizontally.

In another embodiment of the invention the float is of buoyancy suchthat a normal water line of the float defines a third horizontal planein use. Preferably, the first plane defined by the damping means extendsin use at a level spaced apart from and below the third horizontalplane. Alternatively, the first plane defined by the damping meansextends in use at a level coinciding with the third horizontal plane.

In another embodiment of the invention a keel extends from the float forminimising rolling movement of the float.

In a further embodiment of the invention a pair of keels are providedextending from the float.

In one embodiment of the invention each keel defines a correspondingkeel plane. Preferably, the keel planes of the respective keels extendperpendicularly to each other. Advantageously, each keel plane extendsperpendicularly to the first plane defined by the damping means.Ideally, each keel extends along the float and terminates in respectiveends in the damping means.

In one embodiment of the invention each keel is formed by a ribextending from the float, and preferably, each keel is of a rigidmaterial. Ideally, each keel is integrally formed with the float.

In another embodiment of the invention the float defines a first majorplane coinciding with a horizontal plane, which in use extends throughthe float at its maximum horizontal cross-sectional area, and a secondmajor plane coinciding with a vertical plane, which in use extendsthrough the float at its maximum vertical cross-sectional area.Preferably, the first plane defined by the damping means extendsparallel to the first major plane defined by the float. Advantageously,the first plane defined by the damping means is spaced apart from thefirst major plane defined by the float, and preferably, the first planedefined by the damping means extends at a level below the first majorplane defined by the float. Alternatively, the first plane defined bythe damping means coincides with the first major plane defined by thefloat.

In one embodiment of the invention the second major plane defined by thefloat extends at a level spaced apart and below the third plane definedby the waterline. Alternatively, the second major plane defined by thefloat extends at a level coinciding with the third plane defined by thewaterline.

In one embodiment of the invention a coupling means is provided forcoupling the float to a mooring rope.

In another embodiment of the invention the coupling means is located inthe keel. Preferably, the coupling means is located adjacent a lower endof the keel in use.

In a further embodiment of the invention the coupling means is locatedin the damping means. Preferably, a pair of coupling means are provided,and the coupling means are located in the damping means at spaced apartlocations. Advantageously, the respective coupling means are locatedequi-spaced around the float.

Ideally, the keel extends between the respective coupling means.

In one embodiment of the invention each coupling means comprises acoupling plate and at least one bore extending through the couplingplate.

In one embodiment of the invention the damping means comprises at leastone damping plate. Preferably, each damping plate is of a rigidmaterial. Advantageously, the damping means is integrally formed withthe float.

In another embodiment of the invention the float comprises a hollowshell defining an airtight hollow interior region.

In a further embodiment of the invention a valving means is provided inthe shell for facilitating pressurising the hollow interior region witha gaseous medium.

Preferably, the gaseous medium is air.

Advantageously, the hollow shell is of a rigid material.

In another embodiment of the invention the shell of the float is adaptedfor sustaining pressure within the hollow interior region of at leastone and a half atmospheres. Preferably, the shell of the float isadapted for sustaining pressure within the hollow interior region of atleast two atmospheres.

In one embodiment of the invention the float is of ovoid shape, and thefirst major plane defined by the float coincides with a horizontal majorplane of the ovoid, and the second major plane defined by the floatcoincides with a vertical major plane of the ovoid. Preferably, thefloat is of substantially elliptical cross-section when viewed in plan.Advantageously, the float is of circular transverse cross-section whenviewed end on.

In another embodiment of the invention the float is of substantiallyspherical shape. Preferably, the float is of circular transversecross-section when viewed in plan. Advantageously, the float is ofslightly ovoid vertical cross-section.

In another embodiment of the invention a plurality of spaced apartradially extending reinforcing fillets extend between the float and thedamping means for strengthening the joint between the damping means andthe float.

In a further embodiment of the invention a plurality of spaced apartribs extend radially outwardly and around the float parallel to a fourthplane defined by the float which extends transversely of the first andsecond planes defined by the float.

In one embodiment of the invention the float is adapted for securing toand supporting a tethering rope which is adapted for suspending cropropes therefrom. Preferably, the float is adapted for supporting a pairof spaced apart tethering ropes, with the float located between therespective tethering ropes.

In another embodiment of the invention a pillar extends upwardly fromthe float.

In a further embodiment of the invention the float is adapted for use asa navigational buoy.

In another embodiment of the invention the pillar terminates in areceiving means for receiving any one or more of a beacon, a radarreflector and instrumentation. Preferably, any one or more of thebeacon, radar reflector and instrumentation is mounted on the receivingmeans, and preferably, the instrumentation is selected from any one ormore of the following:

-   -   a temperature sensor,    -   a wind speed sensor,    -   a wind direction sensor,    -   a humidity sensor,    -   an ambient air pressure sensor.

Advantageously, the pillar is integrally formed with the float.

In one embodiment of the invention the float is of plastics material andpreferably, the float is formed by rotational moulding.

The invention also provides a floatable structure comprising the floataccording to the invention, and a pillar extending upwardly therefrom.

In one embodiment of the invention the pillar is adapted so that thefloatable structure is suitable for use as a navigational buoy.

In another embodiment of the invention the pillar terminates in areceiving means for receiving any one or more of the following:

-   -   a beacon,    -   a radar reflector,    -   instrumentation.

In a further embodiment of the invention any one or more of thefollowing are mounted on the receiving means:

-   -   a beacon,    -   a radar reflector,    -   instrumentation.

Preferably, the instrumentation comprises any one or more of thefollowing:

-   -   a temperature sensor,    -   a wind speed sensor,    -   a wind direction sensor,    -   a humidity sensor,    -   an ambient air pressure sensor.

In one embodiment of the invention ballast is provided for ballastingthe floatable structure. Preferably, the ballast is located within thefloat.

The invention also provides a method for damping buoyant movement of afloat in water in a generally vertical direction, the method comprisingproviding a damping means extending laterally from the float.

Preferably, the damping means extends from a surface of the float, whichin use is submersed.

Advantageously, a keel is provided extending from the float forminimising rolling of the float.

Preferably, the float is provided in the form of a hollow shell definingan airtight hollow interior region, and the method further comprisespressurising the hollow interior region thereof with a gaseous medium,and advantageously, the hollow interior region is pressurised to apressure of at least one and a half atmospheres, and ideally, the hollowinterior region is pressurised to a pressure of at least twoatmospheres.

In another embodiment of the invention the method further comprisesproviding a coupling means on the float for coupling the float to one ofa tethering rope and a mooring rope.

The invention also provides a method for growing marine molluscs, themethod comprising supporting an elongated tethering rope on a pluralityof spaced apart floats according to the invention, and suspending cropropes impregnated with a spawn of the marine molluscs from the tetheringrope and/or the floats.

Preferably, a pair of spaced apart tethering ropes are supported by aplurality of the spaced apart floats coupled to and extending betweenthe tethering ropes, and crop ropes being suspended from the respectivetethering ropes and/or the floats.

The advantages of the invention are many. In particular, buoyantmovement of the float and the submersible structure according to theinvention in a generally vertical direction is damped, and inparticular, upward buoyant movement of the float and floatable structureafter submersion thereof is damped. The damping means of the float andthe floatable structure damps the effect of the upward buoyant forceexerted on the float or floatable structure when submerged, and inparticular when submerged to significant depths, resulting from wavemotion in stormy seas. Accordingly, the damping means minimises theeffect of the upward propulsion forces to which the float or floatablestructure is subjected when submerged, and in particular, when submersedby waves in stormy conditions. By minimising the effect of the upwardpropulsion forces on the float and floatable structure, the height towhich the float or floatable structure is projected out of and above thewater by the propulsion forces is minimised, and in many cases theupward movement is sufficiently damped to avoid the float or floatablestructure being propelled out of the water. Thus, where the float orfloatable structure is moored by a mooring rope to a sea bed, lake bed,river bed or the like, any danger of a mooring rope being snapped as aresult of the upward propulsion force to which the float or floatablestructure is subjected is minimised and in general avoided.

Additionally, where the float according to the invention is used forsupporting tethering ropes from which crop ropes are suspended forgrowing marine molluscs and the like, by damping the upward movement ofthe float resulting from the buoyant upward propulsion forces to whichthe float is subjected when submerged in the water in stormy conditions,upward movement of the crop ropes is damped to the extent that the cropropes, in general, are not propelled from the water by the upwardbuoyant propulsion forces on the floats. This, thus, minimises thedanger of marine molluscs being lost from the crop ropes by, forexample, being shaken therefrom. Additionally, damping the upwardvertical movement, and indeed, the downward vertical movement of thefloats also minimises any danger of the crop ropes rubbing against eachother, thereby minimising any danger of marine molluscs being detachedtherefrom. These advantages are derived by virtue of the fact that thefloat and floatable structure according to the invention are providedwith the damping means.

The provision of a keel further enhances the effect of the dampingmeans, since the provision of a keel minimises rolling of the float orfloatable structure, thereby maximising the vertical upward and downwarddamping effect of the damping means on vertical movement of the float orfloatable structure.

Additionally, since the damping means also damps downward verticalmovement of the float or floatable structure according to the inventionin stormy conditions where the float or floatable structure is likely tobe submerged, the depth to which the float or floatable structure issubmerged is minimised, and thus, by minimising the depth to which thefloat or floatable structure is submerged, the upward buoyant propulsionforces to which the float or floatable structure are subjected arelikewise minimised. Indeed, by damping the downward movement of thefloat according to the invention, in may cases a wave will have passedbefore the float is submerged to any significant depth, thereby furtherminimising the upward buoyant force to which the float is subjected, andthus minimising any danger of the float being propelled out of thewater.

Pressurising the hollow interior region of the float or floatablestructure has the added advantage that the danger of the float orfloatable structure collapsing while submerged is minimised, and ingeneral is eliminated, and thus, even where the float or floatablestructure is submerged in excessively stormy conditions to relativelygreat depths, in general, the float or floatable structures according tothe invention survives such submersion.

Where the float or floatable structure according to the invention isused for carrying instrumentation, and in particular, sensitiveinstrumentation, by damping the upward vertical movement of the floatand floatable structure, the effect of the buoyant upward propulsionforces on the float and floatable structure is minimised, thusminimising shocks to which the instrumentation carried on the float orfloatable structure are subjected.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood from the followingdescription of some preferred embodiments thereof which are given by wayof example only with reference to the accompanying drawings in which:

FIG. 1 is a top perspective view of a float according to the invention,

FIG. 2 is a partly cutaway underneath perspective view of the float ofFIG. 1,

FIG. 3 is a side elevational view of the float of FIG. 1,

FIG. 4 is a top plan view of the float of FIG. 1,

FIG. 5 is an underneath plan view of the float of FIG. 1,

FIG. 6 is a front end elevational view of the float of FIG. 1,

FIG. 7 is a rear end elevational view of the float of FIG. 1,

FIG. 8 is a perspective view of a plurality of the floats of FIG. 1 inuse,

FIG. 9 is an enlarged perspective view of one of the floats of FIG. 1,in use,

FIG. 10 is a perspective view of a float according to another embodimentof the invention,

FIG. 11 is a front elevational view of the float of FIG. 10,

FIG. 12 is a side elevational view of the float of FIG. 10,

FIG. 13 is a top plan view of the float of FIG. 10,

FIG. 14 is an underneath plan view of the float of FIG. 10,

FIG. 15 is a perspective view of a float according to a furtherembodiment of the invention,

FIG. 16 is a perspective view of a navigational buoy according to theinvention,

FIG. 17 is a front elevational view of the navigational buoy of FIG. 16,

FIG. 18 is a top plan view of the navigational buoy of FIG. 16,

FIG. 19 is an underneath plan view of the navigational buoy of FIG. 16,

FIG. 20 is a perspective view of a portion of the navigational buoy FIG.16, and

FIG. 21 is another perspective view of the portion of the navigationalbuoy of FIG. 16.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings and initially to FIGS. 1 to 9 there isillustrated a float according to the invention indicated generally bythe reference numeral 1, which in this embodiment of the invention issuitable for use in the growing of marine molluscs, and in particularfor use in commercial mussel growing, for locating and coupling betweena pair of longitudinally extending spaced apart parallel tethering ropes2 and for suspending crop ropes 3 impregnated with mussel spawnsubmersed in seawater on which mussels are grown, see FIGS. 8 and 9. Thefloat 1 in this embodiment of the invention is of plastics material, andmay be of low-density polyethylene or high-density polyethylene materialand is formed by rotational moulding, although the float may be formedby blow moulding or by other suitable plastics materials formingprocesses. The float 1 comprises a hollow ovoid shell 5 which defines anairtight hollow interior region 6, and the shell 5 is of strengthsufficient to withstand the hollow interior region 6 being pressurisedby compressed air to a pressure of approximately two atmospheres. Theshell 5 defines first and second major central planes 8 and 9 which areperpendicular to each other, the first major central plane 8 extendinghorizontally, in use, and coinciding with a plane, which in use extendslongitudinally through the float 1 at its maximum horizontallongitudinal cross-sectional area, and the second major central plane 9extending vertically, in use, and coinciding with a plane which in useextends longitudinally through the float 1 at its maximum verticallongitudinal cross-sectional area. The normal waterline of the float 1defines a third horizontal plane, in use, which in this embodiment ofthe invention coincides with the first major central plane. A fourthplane, which in this embodiment of the invention is a minor centralplane 10 defined by the shell 5 coinciding with a plane extendingtransversely through the float 1 at its maximum vertical transversecross-sectional area in use, extends perpendicularly to both the firstand second major central planes 8 and 9.

A damping means for damping upward and downward vertical movement of thefloat 1 comprises a damping plate 12 extending laterally outwardly fromand around the shell 5. The damping plate 12 defines a first plane 14which extends parallel to the first major central plane 8 and is spacedapart below the first major central plane 8. Thus in this embodiment ofthe invention the damping plate 12 extends from a lower portion 15 ofthe surface 16 of the shell 5, which in use, in general, is below thenormal waterline of the float and is submersed. Accordingly, the dampingplate 12 is in normal use located within the water for damping upwardbuoyant movement of the float 1 in the water. However, prior tocommencement of growing of the crop and during the early stages of cropgrowth, when the weight of the crop ropes is less than their weight asthe crop develops, the damping plate may not be submerged in calm water.

A longitudinally extending keel 18 extends radially outwardly anddownwardly from the shell 5 from a front end 19 to a rear end 20 of theshell 5 for minimising rolling of the float 1 in water. The keel 18defines a keel plane which coincides with the second major central plane9, and accordingly, the keel plane defined by the keel 18 isperpendicular to the first plane 14 defined by the damping plate 12.

A pair of coupling means comprising a pair of coupling plates 22 extendaxially outwardly at the respective front and rear ends 19 and 20 of theshell 5 for coupling the float 1 to the tethering ropes 2. The couplingplates 22 are located in and form part of the damping plate 12 at therespective front and rear ends 19 and 20 of the float 1. Two bores 23extend through each coupling plate 22 for coupling the float 1 to thetethering ropes 2. The keel 18 extends from and between the respectivecoupling plates 22.

A plurality of spaced apart radially extending first reinforcing fillets25 reinforce the joint of the damping plate 12 to the shell 5. Secondreinforcing fillets 26 at the front and rear ends 19 and 20 reinforcethe joints of the coupling plates 22 to the shell 5. A plurality ofreinforcing hoop ribs 27 extend around the shell 5, and definerespective planes which extend parallel to the minor central plane 10. Alongitudinally extending reinforcing rib 28 extends along the top of theshell 5 from the front end 19 to the rear end 20 for strengthening theshell 5.

A valving means, namely, a valve 29 is located in a boss 30 forfacilitating pressurising the hollow interior region 6 with compressedair.

In use a plurality of the floats 1 are pressurised with compressed airto a pressure of two atmospheres. The floats 1 are tethered at spacedapart intervals along and between a pair of longitudinally extendingspaced apart parallel tethering ropes 2 by securing the tethering ropes2 to the coupling plates 22 for supporting the tethering ropes 2 in thewater. The tethering ropes 2 as will be understood by those skilled inthe art are secured at respective opposite ends to suitable moorings.Crop ropes 3 impregnated with mussel spawn are secured at spaced apartintervals to the respective tethering ropes 2, and depend downwardlytherefrom, and are submerged in the sea. The damping plate 12 asmentioned above extends from the submersible portion 15 of the float 1,and with each float 1 coupled to the tethering ropes 2 with its keel 18extending downwardly, in general, the damping plate 12 is submersed inthe water.

When the floats 1 are subjected to stormy conditions with relativelyhigh waves, the floats 1 become submerged and may become submerged todepths of up to twenty metres and more, although the damping plate 12also damps downward movement of the floats 1, and thus the floats 1 arenot submerged to the same depths as floats known heretofore for the samesea conditions. However, the upwardly directed buoyant propulsion forceacting on the floats 1 which urge the floats 1 upwardly from such depthsis significantly damped by the damping plate 12, and upward movement ofthe floats 1 under the action of the buoyant propulsion force isretarded, thereby avoiding the floats 1 being propelled out of the wateras they are being returned to their normal flotation level.

The performance of a float according to this embodiment of the inventionof size of 400 litres was tested against a similar float without adamping plate. The width of the damping plate 12 of the float accordingto the invention was 6.25 cm. Both floats were submerged to a depth ofone metre in water. The float without the damping plate rose to thesurface one second after being released, while the float according tothis embodiment of the invention took three seconds to reach the surfaceafter being released. Accordingly, the provision of the damping platesignificantly retards upward movement of the float according to theinvention.

Even in exceptionally stormy conditions if the damping provided by thedamping plate 12 is insufficient to prevent the floats 1 being propelledfrom the water, the speed at which the floats are propelled from thewater is sufficiently retarded that any travel of the floats 1 above thesurface of the water is sufficiently retarded, and the height to whichthe floats 1 travel out of the water is sufficiently reduced to minimisethe danger of mussels growing on the crop ropes 3 being shaken from theropes 3.

Additionally, the damping plate 12 by limiting the amount of upward anddownward movement of the floats, brushing of the crop ropes against eachother is either eliminated or at least significantly reduced, andtherefore, loss of mussels from the crop ropes 3 by inter-rope frictionis also eliminated, or at least significantly reduced over and abovesystems known heretofore. It should be noted that all references todownward movement of the floats according to the invention are to beunderstood as being downward movement of the floats relative to thesurface of the water and to the surface of a wave.

By pressurising the hollow interior region 6 of the shell 5 of thefloats 1 to two atmospheres any danger of the floats 1 collapsing underpressure at relatively deep depth is minimised, and in general, avoided.

By providing the keel 18 on the floats 1, rolling of the floats 1 in thewater is minimised, and accordingly, the damping plate 12 of the floats1 is therefore retained extending substantially horizontally from theshell 5 of the floats 1 at virtually all times, thus maximising thevertical damping effect of the damping plate 12 on each float 1.

Additionally, by locating the coupling plates 22 to form part of thedamping plate 12 of each float, the coupling plates 22 are located onthe submersible portion of the surface of the floats 1, and thus, innormal operation are below the water line of the floats 1. This providesthe added advantage that since the tethering ropes 2 are coupled to thecoupling plates 22 which are below the water line, the tethering ropes 2are also located below the water line, and thus, there is little or nodanger of floating debris chaffing or cutting the tethering ropes 2.This is a particular advantage in arctic and semi-arctic waters wherefloating ice can have a serious detrimental chaffing action on tetheringropes where the tethering ropes extend from the floats at a level at orabove the water line of the floats. Additionally, by virtue of the factthat the tethering ropes extend from the floats below the water line ofthe floats, the crop ropes similarly are suspended from the tetheringropes below the surface of the water, and thus, there is little or nodanger of floating debris, ice or the like chaffing the crop ropes.

It is envisaged that where the floats according to the invention areprovided for mussel growing, they will be provided in sizes of from 250litres to 400 litres, and may be provided in larger or smaller sizes.Typically, the width of the damping plate will be dependent on the sizeof the float, and in general, will range from 5 cm to 8 cm.

Referring now to FIGS. 10 to 14 there is illustrated a float accordingto another embodiment of the invention indicated generally by thereference numeral 40. The float 40 is somewhat similar to the float 1and similar components are identified by the same reference numeral. Themain difference between the float 40 ant the float 1 is in the shape ofthe float, and the location of the coupling plate. In this embodiment ofthe invention the float 40 comprises a hollow shell 5 which is formed ofplastics material by rotational moulding, and is substantiallyspherical. When viewed in plan the shell 5 is of circular cross-section,and when viewed in elevation is of slightly elliptical cross-section. Adamping means for damping upward and downward movement of the float inthe water comprises a circular annular damping plate 41 which extendslaterally from and around the shell 5 at a location corresponding to thelocation of maximum diameter of the shell 5, which in use, in generally,is below the normal waterline of the float 40.

A pair of keels 42 formed by ribs 43 extend generally downwardly fromthe shell 5 for minimising pitching and rolling of the float 40. Theribs 43 forming the keels 42 extend between opposite sides of the shell5 adjacent the damping plate 41, and define respective keel planes whichare perpendicular to each other, and extend perpendicularly from a firstplane defined by the damping plate 41. The keel planes defined by therespective keels 42 each bisect the float 40.

In this embodiment of the invention only one single coupling plate 44 isprovided and extends downwardly from one of the keels 42, and isincorporated in the ribs 43 forming the keel 42. A single bore 45extends through the coupling plate 44 for securing to a tethering rope,an anchor rope, cable or chain, or for receiving a rope impregnated withmuscle spawn which in use would depend downwardly from the float 40.

Strengthening ribs 46 are provided on a top portion of the shell 5 forstrengthening the shell 5.

Otherwise, the float 40 is similar to the float 1, and may or may not bepressurised. Where the float 40 is to be pressurised, a suitablepressurising valve (not shown) is provided in the shell 5 similar tothat already described with reference to the float 1.

Use of the float 40 is somewhat similar to the float 1, with theexception that in generally, the float 40 will be used in conjunctionwith ropes, cables or chains depending downwardly therefrom, and may beused for suspending crop ropes impregnated with muscle spawn for growingmuscles, or other shellfish, and may also be used as a marker buoy formarking the location of, for example, lobster pots, crab cages on thesea bed, or other such cages and pots on the bed of a lake or river.Alternatively, the float 40 may be used for supporting and marking thelocation of an anchor rope, cable or chain. The damping plate 41minimises upward and downward movement of the float 40 in the water,while the keels 42 minimise rolling and pitching of the float 40.Additionally, it has been found that the damping plate 41 also assistsin minimising rolling and pitching of the float 40.

Referring now to FIG. 15 there is illustrated a float according toanother embodiment of the invention indicated generally by the referencenumeral 50. The float 50 is substantially similar to the float 40, andsimilar components are identified by the same reference numeral. Theonly difference between the float 50 and the float 40 is in the couplingplate 44, which in this embodiment of the invention is provided with apair of bores 51 for accommodating a pair of tethering ropes, cables orchains. Use of the float 50 is substantially similar to that describedwith reference to the float 40 and the float 1.

It is envisaged that the floats described with reference to FIGS. 10 to15 will be of size in the range of 200 litres to 400 litres, and thedamping plate will be of width of the order of 5 cm to 6.5 cm.

Referring now to FIGS. 16 to 21 there is illustrated a floatablestructure provided as a navigational buoy also according to theinvention and indicated generally by the reference numeral 60. Thenavigational buoy 60 in this embodiment of the invention is particularlysuitable for use as a navigational marker buoy for marking a shippinglane or channel, and is also suitable for carrying a beacon, radarreflector or the like for marking a shipping hazard, and is alsosuitable for carrying instrumentation, such as for example, weathermonitoring instrumentation, such as a device for monitoring wind speed,wind direction, atmospheric air pressure, temperature, humidity or otherproperties of the environment. In this particular embodiment of theinvention the navigational buoy 60 comprises a lower float 61, which issomewhat similar to the float 40, and also comprises a pillar 62extending upwardly from the lower float 61. The lower float 61 andpillar 62 are of hollow construction, and are integrally formed ofplastic material by rotational moulding. The lower float 61 comprises ahollow shell 63, formed by a lower inverted conical shaped portion 64,and an upper portion 65 comprising a cylindrical portion 67 and upwardlytapering portion 68 which extends to a location 69. The pillar 62, whichis also of hollow construction extends upwardly from the location 69 andterminates in a receiving means, in this case, a platform 70 forcarrying instrumentation, a beacon or a radar reflector or the like aswill be described below.

A damping means, in this embodiment of the invention comprises acircular annular damping plate 71 which extends laterally from andaround the shell 63 intermediate the lower conical shaped portion 64 andthe cylindrical portion 67. The damping plate 71 extends from the shell63 at a location below the waterline of the floatable structure innormal use. Reinforcing ribs 72 reinforce the damping plate 71 to thecylindrical portion 67 of the shell 63. A single keel 74 extendingdownwardly from the lower conical portion 64 is formed by a pair of ribs75 which extend downwardly along and on opposite sides of the lowerconical shaped portion 64 from the damping plate 71. In this embodimentof the invention the coupling means is formed by a lower portion of thekeel 74 at 76, and a single bore 78 extends through the keel 74 at 76for accommodating an anchoring rope, cable or chain for locating thenavigational buoy 60 at an appropriate location.

In this embodiment of the invention the navigational buoy 60 isillustrated carrying a beacon 80 and a radar reflector 81. The radarreflector 81 is mounted on the platform 70, and the beacon 80 is mountedon the radar reflector 81. The navigational buoy 60 could, as discussedabove, be used for carrying any other type of beacon, radar reflector,or instrument.

Use of the navigational buoy 60 is substantially similar to use of thefloats 40 and 50 which have already been described. The damping plate 71damps upward and downward movement of the navigational buoy 60 in thewater, and the keel 74 damps rolling movement of the navigational buoy60. Additionally the damping plate 71 also has an affect on minimisingrolling and pitching of the navigational buoy 60.

If desired, the navigational buoy 60 may be provided with ballast forstabilisation of the navigational buoy 60. Where ballast is provided,the ballast will, in general, be located within the hollow interiorregion of the lower float 61 in the lower portion of the lower invertedconical shaped portion 64. Alternatively, the ballast may be suspendedfrom the lower portion of the keel 46 at 76 which forms the couplingmeans, or indeed, the ballast may be incorporated in the keel adjacentthe portion 76.

It is also envisaged that ballast may be provided in the floats of FIGS.1 to 15, and in which case, the ballast would typically be located inthe hollow interior region of the floats adjacent a lower portionthereof, or may be suspended from the keel.

While the floats and the navigational buoy described with reference toFIGS. 1 to 21 have been described as having a normal waterline defininga third plane which coincides with the first major central plane, it isenvisaged in certain cases that the third plane defined by the normalwaterline may be spaced apart above or below the second major centralplane, although, in general, it is desirable that the third planedefined by the normal waterline should coincide with or be spaced apartabove the first major central plane. It will also be appreciated thatwhile the first plane defined by the damping plate has been described asbeing at a level below the first major central plane, in certain cases,it is envisaged that the first plane defined by the damping plate maycoincide with the first major central plane.

While the floats and the navigational buoy have been described as beingof a plastics material, it is envisaged that the floats and navigationalbuoy may be of any other suitable material besides plastics material,and indeed, in many cases may be provided of a metal material, timber,glass, fibreglass or indeed, any other suitable material. It is alsoenvisaged that while the floats and the navigational buoy have beendescribed as being formed by rotational moulding, where the floats andthe navigational buoy are provided of a plastic material, they may beformed by any other suitable plastics forming process.

Additionally, while the damping plates have been described as extendingcompletely around the floats and the navigational buoy, while this isdesirable, it is not essential. However, it is important that thedamping plate should extend from respective opposite sides of the shellof the floats and the navigational buoy. It is envisaged in certaincases, that two or more damping plates spaced apart from each other maybe provided at different vertical levels extending from the float ornavigational buoy. It will also be appreciated that while the keel ofthe float of FIGS. 1 to 9 has been described as extending from andbetween the coupling plates, while this is desirable it is notessential. The keel could be considerably shorter, as could the keels ofthe floats of FIGS. 10 to 15 and the navigational buoy of FIGS. 16 to21.

While the floats of FIGS. 1 to 15 have been described as being suitablefor use in the growing of mussels, it will be appreciated that thefloats of FIGS. 1 to 15 may be used for growing any other marinemolluscs. Additionally, it will be appreciated that the floats of FIGS.1 to 15 may be provided for carrying instrumentation, for example,instrumentation for monitoring weather conditions at sea or the like,such as wind speed and direction, rainfall amounts, temperature,humidity, air pressure and the like. In such cases, the instrumentationsmay be mounted in or on the shell of the float. When the floats are usedfor carrying instrumentation, it is envisaged that the floats will be ofa larger size than the floats for supporting mussel crop ropes. It isalso envisaged that the floats of FIGS. 1 to 15 may be used for markingshipping lanes and areas which are hazardous to shipping, and in whichcase, the floats may carry lights, which may be battery powered or solarpowered.

It is also envisaged that the floatable structure may be a relativelylarge structure, which could be used as a weather station in the sea, orindeed, a semi-submersible structure which could be of the type whichwould include accommodation for people living at sea, for example,involved in the recovery of oil from undersea oil wells, or may beprovided as a semi-submersible structure of the type used in conjunctionwith recovering oil and gas from undersea oil wells. In which case, itis envisaged that the floatable structure would be provided with ballastwhich would be typically located within the hollow interior region ofthe floatable structure, and the damping means would typically beprovided extending on respective opposite sides from the structurerelative to the keel of the structure, and preferably, the damping meanswould extend in a fore and aft direction, and ideally, a keel would beprovided extending downwardly from the floatable structure.

While the float and floatable structure have been described as beingsuitable for carrying beacons, radar reflectors and instrumentation formonitoring weather, it will be readily apparent to those skilled in theart that the float and floatable structures according to the inventionmay be used for monitoring any other aspect of the environment, forexample, pollution and the like. It will also be appreciated that whileparticular instrumentation which may be carried by the float orfloatable structure according to the invention has been described, thefloat or floatable structure may carry any other suitable or desirableinstrumentation. Indeed, it is also envisaged that the float may carryrainfall measuring equipment and instrumentation. It is also envisagedthat the float or floatable structure according to the invention maycarry communications apparatus, for example, a radio transmitter fortransmitting data from the instrumentation. It is also envisaged thatthe communications apparatus may include a radio receiver for receivingradio signals for activating the radio transmitter for transmitting datacollected by the instrumentation. Additionally, it will be appreciatedthat the float or floatable structure may be adapted for carrying abattery for powering beacons, instrumentation and the like carried bythe float or floatable structure, and typically, it is envisaged thatthe battery would be carried within the hollow interior region thereof.It is also envisaged that the float or floatable structure may carryapparatus for generating electricity, for example, solar panels,apparatus for generating electricity from wind, wave, tide and/orcurrent motion of the water.

While the floats have been described as being of particular sizes andbeing of sizes within particular size ranges, the floats may be of anyother size and size ranges. Further, it will be appreciated that whiledamping plates of particular widths and width ranges have beendescribed, damping plates of other widths and sizes may be provided.However, in general, the width of the damping plate will be determinedby the size of the float, and also by the amount of damping required.

While the floats have been described as comprising reinforcing fillets25 for reinforcing the joint of the damping plate to the shell of thefloats, it is envisaged in certain cases that the fillets may beomitted.

While the floats and navigational buoys according to the invention havebeen described as being pressurised with compressed air, the floats maybe pressurised with any gaseous or liquid medium. It is also envisagedthat the floats may be filled with an expanded plastics material, and ingeneral, when filled with an expanded plastics material, the expandedplastics material will be closed cell material.

1. A float comprising: a hollow shell having a front end and a rear end,the hollow shell defining an airtight hollow interior region anddefining a first major plane coinciding with a horizontal plane, whichin use extends through the hollow shell at its maximum horizontalcross-sectional area, a damping means extending completely around andlaterally outwardly from the hollow shell on opposite sides thereof fordamping buoyant movement of the hollow shell in water in a generallyvertical direction, the damping means defining a first plane extendingparallel to the first major plane defined by the hollow shell, and apair of coupling means located in the damping means at the front andrear ends of the hollow shell for coupling the float to one of atethering rope and a mooring rope.
 2. A float as claimed in claim 1 inwhich each coupling means comprises a coupling plate, at least one boreextending through the coupling plate.
 3. A float as claimed in claim 1in which the hollow shell defines a submersible surface, and the dampingmeans extends from the submersible surface.
 4. A float as claimed inclaim 1 in which the first plane defined by the damping means is spacedapart from and below the first major plane defined by the hollow shell.5. A float as claimed in claim 1 in which the float is of buoyancy suchthat a normal water line of the float defines a third horizontal planein use, and the first plane defined by the damping means extends in useat a level spaced apart from and below the third horizontal plane.
 6. Afloat as claimed in claim 5 in which the first major plane defined bythe hollow shell extends at a level spaced apart from and below thethird plane defined by the waterline.
 7. A float as claimed in claim 1in which the damping means comprises at least one damping plate of arigid material.
 8. A float as claimed in claim 1 in which a keeldefining a keel plane extends downwardly from the hollow shell forminimising rolling movement of the float.
 9. A float as claimed in claim1 in which a valving means is provided in the hollow shell forfacilitating pressurising the hollow interior region with a gaseousmedium.
 10. A float as claimed in claim 1 in which the hollow shell isof a rigid material.
 11. A float as claimed in claim 1 in which thehollow shell is adapted for sustaining pressure within the hollowinterior region of the hollow shell of at least one and a halfatmospheres.
 12. A float as claimed in claim 1 in which the hollow shellis of ovoid shape, and the first major plane defined by the hollow shellcoincides with a horizontal major plane of the ovoid, and a second majorplane defined by the hollow shell coincides with a vertical major planeof the ovoid.
 13. A float as claimed in claim 12 in which a plurality ofspaced apart ribs extend radially outwardly from and around the floatparallel to a fourth plane defined by the float which extendstransversely of the first and second major planes defined by the float.14. A float as claimed in claim 1 in which a pillar extends upwardlyfrom the float.
 15. A float as claimed in claim 1 in which the float isadapted for supporting a pair of spaced apart tethering ropes, with thefloat located between the respective tethering ropes and with thetethering ropes secured to the coupling means.
 16. A float as claimed inclaim 1 in which the float is of plastics material.
 17. A floatcomprising: a hollow shell having a front end and a rear end, the hollowshell defining an airtight hollow interior region and a first majorplane coinciding with a horizontal plane, which in use extends throughthe hollow shell at its maximum horizontal cross-sectional area, adamping means extending completely around and laterally outwardly fromthe hollow shell on opposite sides thereof for damping buoyant movementof the hollow shell in water in a generally vertical direction, thedamping means defining a first plane extending parallel to the firstmajor plane defined by the hollow shell, and a keel extending downwardlyfrom the hollow shell for minimising rolling movement of the hollowshell, the keel extending along the hollow shell and terminating in thedamping means adjacent the front and rear ends of the hollow shell, anddefining a corresponding keel plane extending perpendicularly to thefirst plane defined by the damping means.
 18. A method for dampingbuoying movement of a float in water in a generally vertical direction,the method comprising: providing a hollow shell having a front end and arear end, the hollow shell defining an airtight hollow interior regionand defining a first major plane coinciding with a horizontal plane,which horizontal plane in use extends through the hollow shell at itsmaximum horizontal cross-sectional area, providing a damping meansextending completely around and laterally outwardly from the hollowshell on opposite sides thereof for damping buoyant movement of thehollow shell in water in a generally vertical direction, the dampingmeans defining a first plane extending parallel to the first major planedefined by the hollow shell, and providing respective coupling meanslocated in the damping means at the front and rear ends of the hollowshell for coupling the float to one of a tethering rope and a mooringrope.
 19. A method for growing marine molluscs, the method comprising:providing a plurality of floats, each float comprising a hollow shellhaving a front end and a rear end, the hollow shell defining an airtighthollow interior region and defining a first major plane coinciding witha horizontal plane, which in use extends through the hollow shell at itsmaximum horizontal cross-sectional area, providing a damping meansextending completely around and laterally outwardly from the hollowshell on opposite sides thereof for damping buoyant movement of thehollow shell in water in a generally vertical direction, the dampingmeans defining a first plane extending parallel to the first major planedefined by the hollow shell, providing a pair of coupling means locatedin the damping means at the front and rear ends of the hollow shell forcoupling the float to one of a tethering rope and a mooring rope,supporting an elongated tethering rope on the plurality of the floatsfloating in water and spaced apart from each other along the tetheringrope by securing the tethering rope to one of the coupling means of eachfloat, and suspending crop ropes impregnated with a spawn of the marinemolluscs from the tethering rope and/or the floats.
 20. A method asclaimed in claim 19 in which a pair of spaced apart tethering ropes aresupported on the floats with the tethering ropes secured to therespective coupling means of each float and with the floats extendingbetween the tethering ropes.